Soak the lentils in the water for one night. Chop the onion, clean and chop the greens, dice the bacon. Fry the bacon and onion until translucent, drain the lentils. Add the greens, lentils and spices to the bacon. Add beef broth and do everything together over medium heat for 1 hour.
Remove the peel from the potatoes and cut them into small cubes. Clean the leek and cut into fine rings. Add both to the soup after 30 minutes of cooking. Season the soup with salt, pepper and vinegar at the end.